Latch lock works from inside

At Cycles Inc. in Sterling, MA, 23 presses, all less than 150 tons, make a variety of pharmacological disposables, cosmetics parts, automotive products, and some computer and business equipment parts. Recently, says vice president Augie Bates, he had to mold a poly-propylene insert for a metal shell for a perfume container. At .875 inch in diameter and 1.5 inches long, it has internal ribs that must be accurate to within plus or minus.002 inch.

Because of the way the mold is configured, says Bates, he couldn't hang any latches or stripping mechanisms off the side of the tool. Looking for a latch to fit in the mold, Bates gave the Precision Latch Lock a try, a simple latch and lock system designed for use in stripper, three-plate, and double ejection/collapsible core molds. "The nice thing," says Bates, "is that the latch lock is completely internal. Nothing hangs outside the mold."

This latch lock, currently manufactured by Precision Plastic Tool in South Windsor, CT, is a three-piece tool that consists of a latch of spring steel, a lock that fits in and is held by the latch, and a pin that runs through both and releases the lock from the latch when the third plate opens. The latch lock installs internally in the mold, and cavities for the device can be machined simply, either when the tool is constructed, or later. Pulling action on the latch lock is inline, with no side loads or side actions; neither the latch nor the lock extends beyond the parting line.

The latch is typically installed in the B side of the mold; the lock is installed in the stripper plate; the pin is installed in the A half of the mold. When the mold is closed, the latch holds the tip of the lock in its spring-loaded fingers; the release pin runs through both. The length of the pin determines the distance the mold opens before the stripper, or third, plate opens. The end of the pin is tapered and when it reaches the spring-steel fingers of the latch, it opens the latch, releasing the lock (see diagrams).

Bates has been using the Precision Latch Lock for four years in molds that average about 50,000 shots per year. He reports no problems to date and says the only maintenance he performs is an occasional oiling of the components. Of his 400 molds, Bates says about 10 have such latches.

At Innovative Mold and Machine in Chicopee, MA, president Steve Young echoes similar sentiments, but for different reasons. "It was a nice alternative," he says. "It was internal, which means we didn't have anything hanging off the side." Young says he likes to use Master Unit Die frames in the mold; the internal latch lock system allows him to change out MUD units at will without worrying about the latch system. "It's a good alternative to allow us to use a different style of mold frame," he reports.

Of the 25 or 30 molds he built in the last year, Young estimates he used the latch lock in about half. He's also gotten creative, in several instances telescoping the pin, or modifying it to move the stripper plate and for transferring parts. Like Bates', his molds average about 50,000 shots. He does note that the latch lock is more expensive than external latching systems he's used, but that "the internal convenience outweighs any cost difference."

The Precision Latch Lock is currently manufactured and sold by Precision Plastic Tool. Roehr Tool (Hudson, MA) is involved in marketing the latch lock for Precision Plastic Tool. Paul Catalanotti, president of Roehr, says you can look for an externally mounted version of the Precision Latch Lock by early 1998.